Vitamin D derivatives and their preparation and application are discussed in many references in the patent and other literature. For example, U.S. Pat. No. 3,565,924 is directed to 25-hydroxycholecalciferol; U.S. Pat. No. 3,697,559 is directed to 1,25-dihydroxycholecalciferol; U.S. Pat. No. 3,741,996 is directed to 1.alpha.-hydroxycholecalciferol; U.S. Pat. No. 3,786,062 is directed to 22-dehydro-25-hydroxycholecalciferol; U.S. Pat. No. 3,880,894 is directed to 1,25-dihydroxyergocalciferol; U.S. Pat. No. 4,201,881 is directed to 24,24-difluoro-1.alpha.,25-dihydroxycholecalciferol; U.S. Pat. No. 4,196,133 is directed to 24,24-difluoro-1.alpha.,25-dihydroxycholecalciferol.